SUNDAY, May 30 (HealthDay News) -- New research suggests that vitamins may do nothing to protect men against bladder cancer and might even raise the risk of another type of cancer.

In one study examining vitamin use, researchers analyzed more than 10,000 questionnaires that men filled out as they took part in prostate screenings.

More than 60% of the men said they took supplements, with 48% taking three or more. Multivitamins, fish oil, and vitamin C were the most common supplements that the men used.

"The high prevalence of supplement use reported in this study is of potential concern," the study authors wrote. "Previous studies suggest an association between multivitamin use and increased risk of advanced prostate cancer," which the earlier research had linked to men who used multivitamins seven or more times a week.

Researchers also studied 77,719 residents of Washington state, aged 50-76, who filled out surveys in 2000-2002.

Of those, 330 developed bladder cancer over the next five years. Researchers found that vitamin use didn't lower the odds of bladder cancer.

The findings are scheduled to be released Sunday at the annual meeting of the American Urological Association in San Francisco.

"It's really disturbing to think that so many people are taking vitamins, assuming that these pills are providing some sort of health benefits," Dr. Mark A. Moyad, who is moderating a panel where the findings will be discussed, said in a news release. "The reality is that very little scientific research has proven vitamins to be effective in protecting against cancer."